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Type: Artigo de periódico
Title: Double Transacetalization Of Diacylium Ions.
Author: Sparrapan, R
Mendes, M A
Eberlin, M N
Abstract: A novel gas-phase reaction of diacylium ions of the O=C=X(+)=C=O type (X = N, CH) is reported: double transacetalization with cyclic acetals or ketals. The reaction is exothermic and highly efficient, and forms members of a new class of highly charged-delocalized ions: cyclic ionic diketals. Pentaquadrupole double- and triple-stage mass spectrometric (MS(2) and MS(3)) experiments reveal the high double transacetalization reactivity of O=C=N(+)=C=O and O=C=CH(+)=C=O, whereas the synthesis of differently substituted cyclic ionic diketals is performed in MS(3) experiments via sequential mono- and double transacetalization of O=C=N(+)=C=O and O=C=CH(+)=C=O with different acetals. With cyclic acetals, the acylium-thioacylium ion O=C=N(+)=C=S reacts promptly and selectively by mono-transacetalization at its acylium site, but the free thiacylium site of its cyclic ionic ketal is nearly unreactive by double transacetalization. Therefore, only the acylium site of O=C=N(+)=C=S can be efficiently protected by transacetalization. Low-energy MS(3) collision-induced dissociation of the cyclic ionic diketals of O=C=N(+)=C=O and O=C=CH(+)=C=O sequentially frees each of the protected acylium site to form the mono-derivatized ion, and then the fully deprotected diacylium ion.
Subject: Acetals
Mass Spectrometry
Citation: Journal Of Mass Spectrometry : Jms. v. 35, n. 2, p. 189-98, 2000-Feb.
Rights: fechado
Identifier DOI: 10.1002/(SICI)1096-9888(200002)35:2<189::AID-JMS929>3.0.CO;2-I
Date Issue: 2000
Appears in Collections:Unicamp - Artigos e Outros Documentos

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